Gear shifting apparatus for multi-speed transmission for electric vehicles

ABSTRACT

A gear shifting apparatus for a multi-speed transmission includes: a shifting unit controlling gear shifting by a torque of an actuator; and a parking unit controlling a parking state by the torque of the actuator. In particular, the actuator includes a control motor transmitting a driving torque to a first driven gear of the shifting unit and a second driven gear of the parking unit through a drive gear externally gear-meshed with the driven gears, and the shifting unit includes: a fork slider slidably mounted on a fork rail, a shift fork integrally formed with the fork slider, a cam block connected to the first driven gear engaged with the drive gear and having a cam surface on an exterior circumference for shift-stages, a cam contact pin integrally formed with the fork slider and contacting the cam surface, and a return spring mounted around the fork rail.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2018-0144583, filed on Nov. 21, 2018, the entirecontents of which are incorporated herein by reference.

FIELD

The present disclosure relates to a gear shifting apparatus formulti-speed transmission for electric vehicles.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

An automated manual transmission (AMT), a dual clutch transmission(DCT), or a multi-speed transmission for an electric vehicle istypically employed to automatically shift gears with a gear arrangementsimilar to the gear arrangement of a conventional manual transmission.Such a transmission is typically provided with a parking actuator for anautomated parking, as well as a shifting actuator to automatically shiftgears.

A multi-speed transmission of an electric vehicle typically employs ashift-by-wire scheme, where shifting is electronically controlled basedon driver's input signal generated by a driver's operation of a shiftlever or a shift button. Since an electric vehicle may practicallyrealize a continuously variable shifting by controlling an output powerof a drive motor, shift-stages more than two shift stages are nottypically required. Thus, a shifting unit installed in such an electricvehicle utilizes only one or two shift forks.

Such a multi-speed transmission of an electric vehicle employs at leastone control motor as a shifting actuator for realizing the gear shiftingbetween the available shift-stages. In addition, another control motoris separately employed as a parking actuator to control a parking spragfor engaging and releasing a parking gear.

We have discovered that two separate control motors (i.e., the controlmotor for a shifting unit for gear-shifting, and another control motorfor a parking unit for engaging and releasing a parking gear) may causethe complicated structure of a multi-speed transmission, an increase ina production cost due to increased number of required parts, and anincrease of a vehicle weight.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the present disclosureand therefore it may contain information that does not form the priorart that is already known to a person of ordinary skill in the art.

SUMMARY

The present disclosure has been made in an effort to provide a gearshifting apparatus for a multi-speed transmission for an electricvehicle having advantages of realizing both the shifting function andthe parking function shifting unit by a control motor, enabling controlof first and second shift-stages and a parking stage, thereby realizingsimplification of structure, cost reduction due to less number ofrequired parts, and weight reduction.

A gear shifting apparatus for a multi-speed transmission for an electricvehicle may include: a shifting unit controlling gear shifting by atorque of an actuator; and a parking unit including a parking gear andcontrolling engagement and disengagement of the parking gear by thetorque of the actuator. The actuator may include a control motortransmitting a driving torque to a first driven gear of the shiftingunit and a second driven gear of the parking unit through a drive gearexternally gear-meshed with the first and second driven gears. Theshifting unit may include: a fork slider slidably mounted on a forkrail, a shift fork integrally formed with the fork slider and activatingthe gear shifting, a cam block connected to the first driven gearexternally engaged with the drive gear and having a cam surface on anexterior circumference for shift-stages, a cam contact pin integrallyformed with the fork slider and contacting the cam surface formed on anexterior circumference of the cam block, and a return spring mountedaround the fork rail and abutting the fork slider toward the cam block.

The parking unit may further include: a parking sprag having anengagement end facing the parking gear and configured to rotate about anaxis of a sprag shaft and to abut toward a parking release direction bya return spring; a profile drum connected to the second driven gearexternally engaged with the drive gear, and having a profile grooveformed along an exterior circumference of the profile drum; a parkinglever rotatably disposed on around a lever shaft, and having an endmaintaining contact with the profile groove; and a parking rod connectedto a bottom portion of the parking lever and having a cam portioninteracting with an end of the parking sprag distal to the sprag shaft.

A speed reduction may be achieved when the torque of the control motoris transmitted from the drive gear to the first and second driven gears.

A reduction ratio between the drive gear and the second driven gear maybe larger than a reduction ratio between the drive gear and the firstdriven gear.

The parking lever may rotate at an axis of the lever shaft and therebyhorizontally operates the parking rod.

The cam portion of the parking rod may press the end of the parkingsprag to force the engagement end of the sprag to engage with theparking gear.

The profile groove may include a first portion forming a first stagephase for a parking, and a second portion forming a second stage phasefor a parking release. The first stage phase is different from thesecond stage phase in an axial direction of the profile drum.

The cam surface may include a neutral range, a first shift-stage range,and a second shift-stage range along the exterior circumference of thecam block.

In another form, the parking unit may include: a parking gear, a parkingsprag having an engagement end facing the parking gear and configured torotate about an axis of a sprag shaft and to abut toward a parkingrelease direction by a return spring; a finger drum connected to asecond driven gear externally engaged with the drive gear, and having afinger end on an exterior circumference; a parking lug rotatable about acentrally positioned lever shaft and including two lug ends havingdifferent lengths from each other and configured to interact with thefinger end to support or release the finger end along a rotationdirection of the finger drum; and a parking rod connected to a bottomportion of the parking lug and having a cam portion interacting with anend of the parking sprag distal to the sprag shaft.

The parking lug may include a detent unit formed on the lever shaft soas to provide detent feeling during a parking operation and a parkingrelease operation.

The detent unit may include a detent plate fixed to the lever shaft andhaving a groove at an end of the detent plate, and a detent pinsupporting a ball to the groove.

A multi-speed transmission of an electric vehicle of an exemplary formof the present disclosure realizes both the shifting function and theparking function by a control motor while maintaining controlreliability, thereby providing a compact structure, a cost reduction dueto decreased number of required parts, and a weight reduction.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 and FIG. 2 are schematic perspective views respectivelyillustrating a parked state of a gear shifting apparatus for amulti-speed transmission for an electric vehicle according to a firstexemplary form of the present disclosure;

FIG. 3 and FIG. 4 are schematic perspective views respectivelyillustrating first and second shift-stages of a gear shifting apparatusfor a multi-speed transmission for an electric vehicle according to afirst exemplary form of the present disclosure;

FIG. 5 is a schematic perspective view illustrating a parked state of agear shifting apparatus for a multi-speed transmission for an electricvehicle according to a second exemplary form of the present disclosure;and

FIG. 6 and FIG. 7 are schematic perspective views respectivelyillustrating first and second shift-stages of a gear shifting apparatusfor a multi-speed transmission for an electric vehicle according to asecond exemplary form of the present disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

The size and the thickness of each component illustrated in the drawingsare arbitrarily illustrated in the drawings for better understanding andease of description, but the present disclosure is not limited to theillustration. In the drawings, the thicknesses of various portions andregions are enlarged for clarity.

The drawings and description are to be regarded as illustrative innature and not restrictive, and like reference numerals designate likeelements throughout the specification.

In the following description, dividing names of components into first,second and the like is to divide the names because the names of thecomponents are the same as each other and an order thereof is notparticularly limited.

For convenience of description of an exemplary form of the presentdisclosure, directions are described as left and right with a merereference to FIG. 1, and may be understood that such direction isintrinsic to an actual apparatus.

FIG. 1 and FIG. 2 are schematic perspective views respectivelyillustrating a parked state of a gear shifting apparatus for amulti-speed transmission for an electric vehicle according to a firstexemplary form of the present disclosure.

A gear shifting apparatus according to a first exemplary form of thepresent disclosure is described with reference to an example of atwo-staged transmission of an electric vehicle.

It should be noted that a gear shifting apparatus according to a firstexemplary form of the present disclosure may be applied to atransmission other than a two-staged transmission. In this case, anadditional shifting unit and/or an additional control motor may beemployed for further number of shift-stages.

Referring to FIG. 1 and FIG. 2, a gear shifting apparatus includes: anactuator, a shifting unit SU receiving a torque from the actuator andcontrols gear shifting through a shift fork 3 installed on a fork rail1, and a parking unit PU receiving a torque from the actuator andcontrolling engagement and disengagement of a parking gear 33 through aparking sprag 31.

The actuator includes a control motor M driving a drive gear DGexternally gear-meshed with driven gears PG1 and PG2 (i.e., a firstdriven gear PG1 of the shifting unit SU, and a second driven gear PG2 ofthe parking unit PU).

The shifting unit SU and the parking unit PU convert the torque of thecontrol motor M to horizontal forces to operate of the shift fork 3 andthe parking sprag 31.

The drive gear DG is mounted on a rotation shaft S of the control motorM.

The shifting unit SU includes a fork slider 5, a shift fork 3, a camblock 9, a cam contact pin 7, and a return spring RS1.

The fork slider 5 is slidably mounted on a fork rail 1 fixed to atransmission housing (not shown).

The shift fork 3 is integrally formed to a lower part of the fork slider5 slidable along the fork rail 1, and enables synchronizer operation.The shift fork 3 is connected to the sleeve (not shown) of thesynchronizer (not shown) for shifting to the first shift-stage and thesecond shift-stage.

A cam surface CF is formed on an exterior circumference of the cam block9, and is connected to a first connecting shaft S1 forming a rotationcenter of the first driven gear PG1 externally engaged with the drivegear DG.

The drive gear DG and the first driven gear PG1 form a reduction gearratio such that a speed reduction is realized when the torque of thecontrol motor M is transmitted to the cam block 9.

The cam block 9 converts the torque of the control motor M to ahorizontal force through the curve of the cam surface CF and transmitsthe horizontal force to the shifting unit SU as driving forces.

The cam surface CF is formed on the exterior circumference of the camblock 9, and includes a neutral range N, a first shift-stage range D1,and a second shift-stage range D2.

The cam contact pin 7 is integrally formed in an upper part of the forkslider 5, and maintains contact with the cam surface CF formed on theexterior circumference of the cam block 9.

The return spring RS1 is formed as a coil spring mounted around the forkrail 1. One end of the return spring RS1 is supported by a fixture suchas the transmission housing (not shown), and another end of the returnspring RS1 elastically abuts the fork slider 5 toward the cam block 9,such that the cam contact pin 7 may maintain contact with the camsurface CF of the cam block 9.

The parking unit PU includes a parking gear 33 installed on an outputshaft or an intermediate shaft in a transmission, a parking sprag 31, aprofile drum 51, parking lever 37, and a parking rod 39.

The parking sprag 31 includes an engagement end 31 a protruding from theparking sprag 31 and engaged with teeth of the parking gear 33, anddisposed such that the engagement end 31 a may face the parking gear 33.The parking sprag 31 is fixed to a sprag shaft 41.

A return spring RS2 mounted around the sprag shaft 41 always applies anelastic force on the parking sprag 31 in a parking release direction.

The profile drum 51 is rotated by the torque of the control motor M bybeing connected to a second connecting shaft S2 fixed to a second drivengear PG2 externally engaged with the drive gear DG, and a profile groove53 is formed on an exterior circumference of the profile drum 51.

Along the exterior circumference of the profile drum 51, the profilegroove 53 is formed with different phases in an axial direction. In oneform, the profile groove may include a first portion forming a firststage phase 53 a for a parking, and a second portion forming a secondstage phase 53 b for a parking release.

That is, the first stage phase 53 a of the profile groove 53 is aportion for the parking, and the second stage phase 53 b of the profilegroove 53 is a portion for the parking release. The second stage phase53 b is illustrated to be formed rightward in comparison with the firststage phase 53 a in FIG. 2.

The drive gear DG and the second driven gear PG2 form a reduction gearratio such that a speed reduction is realized when the torque of thecontrol motor M is transmitted to the profile drum 51.

Gear ratios of the drive gear DG and the first and second driven gearsPG1 and PG2 are set such that a reduction ratio between the drive gearDG and the first driven gear PG1 is larger than a reduction ratiobetween the drive gear DG and the second driven gear PG2.

The parking lever 37 is rotatably mounted on the lever shaft 43 fixed tothe transmission housing (not shown), and maintains contact with theprofile groove 53 by the return spring RS3 mounted around the levershaft 43.

A cam portion 39 a is formed on the parking rod 39 at a locationcorresponding to a front end of the parking sprag 31, and a rear end ofthe parking rod 39 is connected to a bottom end of the parking lever 37.

When the parking lever 37 rotates around an axis of the lever shaft 43,the parking rod 39 is horizontally operated. In this case, the camportion 39 a of the parking rod 39 presses an end of the parking sprag31 that is rotatable around an axis of the sprag shaft 41, such that theengagement end 31 a is engaged with the parking gear 33. The cam portion39 a is provided with a conical lateral surface to enable smoothrotation of the parking sprag 31 when the parking rod reciprocates.

The cam surface CF is formed such that while the shifting unit SU staysin the neutral range N, the parking unit PU stays in the first stagephase 53 a of the profile groove 53. And, while the shifting unit SUstays in the first shift-stage range D1 and the second shift-stage rangeD2, the parking unit PU stays in the second stage phase 53 b of theprofile groove 53.

FIG. 3 and FIG. 4 are schematic perspective views respectivelyillustrating first and second shift-stages of a gear shifting apparatusfor a multi-speed transmission for an electric vehicle according to afirst exemplary form of the present disclosure.

Referring to FIG. 1, FIG. 3, and FIG. 4, operation of a gear shiftingapparatus according to a first exemplary form of the present disclosureis hereinafter described.

According to a gear shifting apparatus according to an exemplary form ofthe present disclosure, a control motor M controls both the shiftingunit SU and the parking unit PU.

The control motor M drives the first and second driven gears PG1 and PG2with a reduction ratio through the drive gear DG. Thereby, gear shiftingis controlled through the shift fork 3 on the shift rail 1, and at thesame time, engagement and disengagement of the parking gear 33 with theparking sprag 31 is also controlled.

Referring to FIG. 1, FIG. 3, and FIG. 4, an operation of the form isdescribed with respect to the parking stage, the first shift-stage, andthe second shift-stage.

[Parking Stage]

Referring to FIG. 1, in the parking stage, the top end of the parkinglever 37 is positioned to the first stage phase 53 a of the profilegroove 53 by the rotation of the profile drum 51 driven by the controlmotor M, and maintains contact with the profile drum 51 by the elasticforce of the return spring RS3.

In this case, the parking rod 39 is located in a forward position to theparking sprag 31. In this case, the cam portion 39 a of the parking rod39 presses the end of the parking sprag 31, and the engagement end 31 aof the parking sprag 31 is engaged with parking gear 33. Therefore, theparking gear 33 becomes fixed in the rotating direction, and the parkedstage is achieved.

In addition, the cam contact pin 7 maintains contact with the neutralrange N of the cam surface CF of the cam block 9. In this state, theshift fork 3 is located in the neutral position on the fork rail 1, andtherefore the neutral state is achieved by moving the sleeve (not shown)of the synchronizer (not shown) for shifting to the first shift-stageand the second shift-stage to the neutral position.

[First Shift-Stage]

Referring to FIG. 3, in the first shift-stage, the profile drum 51 isrotated by the control motor M, and thereby, the top end of the parkinglever 37 is located to the profile groove 53 of the second stage phase53 b of the profile drum 51.

In this case, the parking rod 39 moves backward from the parking sprag31 by the rotation of the parking lever 37. Accordingly, the cam portion39 a of the parking rod 39 escapes from the parking sprag 31, andthereby the engagement of the parking gear 33 with the parking sprag 31is released. Therefore, the parking gear 33 may freely rotate, andthereby, the parking stage is released.

At the same time, by the rotation of the cam block 9 driven by thecontrol motor M, the cam contact pin 7 contacts the first shift-stagerange D1 of the cam surface CF of the cam block 9.

In this case, the shift fork 3 moves to a first shift-stage position onthe fork rail 1, and therefore, the first shift-stage is achieved bymoving the sleeve (not shown) for shifting to the first shift-stage andthe second shift-stage to the first shift-stage position.

[Second Shift-Stage]

Referring to FIG. 4, in the second shift-stage, the cam block 9 furtherrotates by the control motor M from the state of the first shift-stage,and the cam contact pin 7 contacts the second shift-stage range D2 inthe cam surface CF of the cam block 9.

In this case, the shift fork 3 moves to a second shift-stage position onthe fork rail 1, and therefore, the first shift-stage is achieved bymoving the sleeve (not shown) of the synchronizer (not shown) forshifting to the first shift-stage and the second shift-stage to thesecond shift-stage position.

While the profile drum 51 further rotates by the control motor M, theparking lever 37 maintains the contact with the profile groove 53 of thesecond stage phase 53 b of the profile drum 51 by the elastic force ofthe return spring RS3, and therefore, the parking release state ismaintained.

FIG. 5 is a schematic perspective view in a parked state of a gearshifting apparatus for a multi-speed transmission for an electricvehicle according to a second exemplary form of the present disclosure.

Hereinafter, a gear shifting apparatus according to a second exemplaryform of the present disclosure is described in detail with reference toFIG. 5.

A gear shifting apparatus according to a second exemplary form of thepresent disclosure is described with reference to an example oftwo-staged transmission, the same as in the first exemplary form.

The gear shifting apparatus according to a second exemplary form of thepresent disclosure includes, the same as in the first exemplary form, anactuator, a shifting unit SU controlling gear shifting through a shiftfork 3 mounted on a fork rail 1 installed with a return spring RS1 by atorque of an actuator, and a parking unit PU receiving a torque from theactuator and controlling engagement and disengagement of a parking gear33 through a parking sprag 31.

The actuator is the same as in the first exemplary form where a controlmotor M drives a drive gear DG externally gear-meshed with the drivengears PG1 and PG2 of the shifting unit SU and the parking unit PU, andthe shifting unit SU and the parking unit PU convert the torque of thecontrol motor M to horizontal forces to operate of the shift fork 3 andthe parking sprag 31, the same as in the first exemplary form.

A gear shifting apparatus according to a second exemplary form of thepresent disclosure differs from first exemplary form only in thearrangement of the parking unit PU, and the actuator and the shiftingunit SU is the same as in the first exemplary form.

The parking unit PU according to the second exemplary form includes aparking gear 33 installed on an output shaft or an intermediate shaft ina transmission, a parking sprag 31, a finger drum 61, parking lug 65,and a parking rod 39.

The parking sprag 31 includes an engagement end 31 a protruding from theparking sprag 31 and engaged with teeth of the parking gear 33, anddisposed such that the engagement end 31 a may face the parking gear 33.The parking sprag 31 is fixed to a sprag shaft 41.

A return spring RS2 mounted around the sprag shaft 41 always acts anelastic force on the parking sprag 31 in a parking release direction.

The finger drum 61 is rotated by the torque of the control motor M bybeing connected to a second connecting shaft S2 fixed to a second drivengear PG2 externally engaged with the drive gear DG, and a finger end 63is integrally formed on an exterior circumference of the parking drum61.

The drive gear DG and the second driven gear PG2 form a reduction gearratio such that a speed reduction is realized when the torque of thecontrol motor M is transmitted to the finger drum 61.

Gear ratios of the drive gear DG and the first and second driven gearsPG1 and PG2 are set such that a reduction ratio between the drive gearDG and the first driven gear PG1 is larger than a reduction ratiobetween the drive gear DG and the second driven gear PG2.

The parking lug 65 includes a lever shaft 43 centrally positioned androtatably supported by the transmission housing (not shown), and alsoincludes lug ends 67 having different lengths to cooperate with eachother so as to support or release, the finger end 63 according to arotating direction of the finger drum 61.

The parking lug 65 may include a detent unit 71 formed on the levershaft 43 so as to provide detent feeling during a parking operation anda parking release operation.

As the detent unit 71, a detent plate 73 is fixed to the lever shaft 43,and a groove G is formed along an end of the detent plate 73. Inaddition, a ball 77 having a cushion contacts the groove G, and a detentpin 75 fixed to the transmission housing (not shown) supports the ball77.

A cam portion 39 a is formed on the parking rod 39 at a locationcorresponding to a front end of the parking sprag 31, and a rear end ofthe parking rod 39 is connected to a bottom end of the parking lug 65.

When the parking lug 65 rotates around an axis of the lever shaft 43,the parking rod 39 is horizontally operated. In this case, the camportion 39 a of the parking rod 39 presses an end of the parking sprag31 that is rotatable around an axis of the sprag shaft 41, such that theengagement end 31 a is engaged with the parking gear 33. The cam portion39 a is provided with a conical lateral surface to enable smoothrotation of the parking sprag 31 when the parking rod reciprocates.

The parking state is formed when the finger end 63 of the finger drum 61pushes a longer one of the two lug ends 67 of the parking lug 65. Theparking release state is formed when the finger end 63 of the fingerdrum 61 is positioned without interaction between the two lug ends 67 ofthe parking lug 65.

As described above, a gear shifting apparatus according to a secondexemplary form of the present disclosure differs from the firstexemplary form only in that the finger drum 61 and the parking lug 65are employed instead of the profile drum 51 and the parking lever 37 tooperate the parking rod 39 of the parking unit PU. The shifting unit SUand the parking unit PU are controlled by the control motor M to formshifting operations between the parking stage and the first and secondshift-stages, the same as in the first exemplary form.

According to a gear shifting apparatus according to a first, secondexemplary form of the present disclosure, in a multi-speed transmissionof an electric vehicle, actuators of the shifting unit SU and theparking unit PU is simplified as a control motor M while enablingcontrol of first and second shift-stages and a parking stage, therebyrealizing simplified structure, a cost reduction due to less number ofrequired parts, and a weight reduction.

While this present disclosure has been described in connection with whatis presently considered to be practical exemplary forms, it is to beunderstood that the present disclosure is not limited to the disclosedforms. On the contrary, it is intended to cover various modificationsand equivalent arrangements included within the spirit and scope of thepresent disclosure.

<Description of symbols> M: control motor SU: shifting unit PU: parkingunit  1: fork rail  3: shift fork  5: fork slider  7: cam contact pin 9: cam block 31: parking sprag 31a: engagement end 33: parking gear 35:parking cam 37: parking lever 39: parking rod 39a: cam portion 41: spragshaft 43: lever shaft 51: profile drum 53: profile groove 61: fingerdrum 63: finger end 65: parking lug 67: lug end 71: detent unit 73:detent plate 75: detent pin 77: ball

What is claimed is:
 1. A gear shifting apparatus for a multi-speedtransmission for an electric vehicle, comprising: a shifting unitconfigured to control gear shifting by a torque of an actuator; and aparking unit including a parking gear and configured to controlengagement and disengagement of the parking gear by the torque of theactuator, wherein the actuator comprises a control motor transmitting adriving torque to a first driven gear of the shifting unit and a seconddriven gear of the parking unit through a drive gear externallygear-meshed with the first and second driven gears, wherein the shiftingunit comprises: a fork slider slidably mounted on a fork rail; a shiftfork integrally formed with the fork slider and configured to activatethe gear shifting; a cam block connected to the first driven gearexternally engaged with the drive gear, wherein the cam block includes acam surface on an exterior circumference thereof for shift-stages; a camcontact pin integrally formed with the fork slider and contacting thecam surface formed on an exterior circumference of the cam block; and areturn spring mounted around the fork rail and abutting the fork slidertoward the cam block.
 2. The gear shifting apparatus of claim 1, whereinthe parking unit further comprises: a parking sprag having an engagementend facing the parking gear and configured to rotate about an axis of asprag shaft and to abut toward a parking release direction by a returnspring; a profile drum connected to the second driven gear externallyengaged with the drive gear, and having a profile groove formed along anexterior circumference of the profile drum; a parking lever rotatablydisposed on around a lever shaft, and having an end maintaining contactwith the profile groove; and a parking rod connected to a bottom portionof the parking lever, wherein the parking rod includes a cam portioninteracting with an end of the parking sprag distal to the sprag shaft.3. The gear shifting apparatus of claim 2, wherein a speed reduction isachieved when the torque of the control motor is transmitted from thedrive gear to the first and second driven gears.
 4. The gear shiftingapparatus of claim 3, wherein a reduction ratio between the drive gearand the second driven gear is greater than a reduction ratio between thedrive gear and the first driven gear.
 5. The gear shifting apparatus ofclaim 2, wherein the parking lever rotates at an axis of the lever shaftand thereby horizontally operates the parking rod.
 6. The gear shiftingapparatus of claim 2, wherein the cam portion of the parking rod pressesthe end of the parking sprag to force the engagement end of the sprag toengage with the parking gear.
 7. The gear shifting apparatus of claim 2,wherein the profile groove comprises a first portion forming a firststage phase for a parking, and a second portion forming a second stagephase for a parking release, and wherein the first stage phase isdifferent from the second stage phase in an axial direction of theprofile drum.
 8. The gear shifting apparatus of claim 1, wherein the camsurface comprises a neutral range, a first shift-stage range, and asecond shift-stage range along the exterior circumference of the camblock.
 9. The gear shifting apparatus of claim 1, wherein the parkingunit further comprises: a parking sprag having an engagement end facingthe parking gear and configured to rotate about an axis of a spragshaft, and to abut toward a parking release direction by a returnspring; a finger drum connected to the second driven gear externallyengaged with the drive gear, and having a finger end on an exteriorcircumference thereof; a parking lug rotatable about a centrallypositioned lever shaft and including two lug ends having a differentlength from each other, wherein the parking lug is configured tointeract with the finger end to support or release the finger end alonga rotation direction of the finger drum; and a parking rod connected toa bottom portion of the parking lug and having a cam portion interactingwith an end of the parking sprag distal to the sprag shaft.
 10. The gearshifting apparatus of claim 9, wherein a speed reduction is achievedwhen the torque of the control motor is transmitted from the drive gearto the first and second driven gears.
 11. The gear shifting apparatus ofclaim 10, wherein a reduction ratio between the drive gear and thesecond driven gear is greater than a reduction ratio between the drivegear and the first driven gear.
 12. The gear shifting apparatus of claim9, wherein the parking lug comprises a detent unit formed on the levershaft so as to provide detent feeling during a parking operation and aparking release operation.
 13. The gear shifting apparatus of claim 12,wherein the detent unit comprises: a detent plate fixed to the levershaft and having a groove at an end of the detent plate; and a detentpin supporting a ball to the groove.
 14. The gear shifting apparatus ofclaim 9, wherein the cam portion of the parking rod presses the end ofthe parking sprag to force the engagement end of the sprag to engagewith the parking gear.